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JEE Main & Advanced JEE Main Paper (Held On 25 April 2013)

  • question_answer
    A radioactive isotope having a half?life period of 3 days received after 12 days. If 3g of the isotope is left in the container, what would be the initial mass of the isotope?     JEE Main Online Paper ( Held On 25  April 2013 )

    A) 12g                                        

    B) 36g

    C) 48g                                        

    D) 24g

    Correct Answer: C

    Solution :

    Given\[{{t}_{1/2}}=3\] Total time T= 12 No. of half lives \[(n)=\frac{12}{3}=4\] \[{{\left( \frac{1}{2} \right)}^{n}}=\frac{N}{{{N}_{o}}}\]\[\therefore \] \[{{\left( \frac{1}{2} \right)}^{4}}=\frac{3}{N}\] \[\frac{3}{N}=\frac{1}{16}\]         \[N=48g\]


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